This invention lies in the field of towing apparatus for connecting the forward portion of a trailer mounted on road wheels to the aft portion of a towing vehicle. It is directed to such apparatus for towing the type of trailer which has only one wheel at each side or two wheels so closely spaced fore and aft that it is not stable in pitch and must rely on a vertical load relationship with the towing vehicle to maintain its proper attitude. It is more particularly directed to such apparatus in which the towing linkage is connected at the aft end of the towing vehicle but functions as if it were connected directly above the rear axle of the vehicle.
Presently "two wheel" type trailers, including those which have two wheels closely spaced fore and aft at each side, are coupled to the tow vehicles by means of a longitudinal tongue fixedly connected to the trailer and connected at its forward end to the rear of a towing vehicle with a ball joint or other type of pivotal device.
For special purpose towing vehicles such as a truck tractor, and also with the conventional type of pickup truck, there is clear space directly above the rear axle, and a pivotal mounting may be readily secured at such location. The forward end of the tongue is connected to the pivotal mounting to form what is commonly referred to as a fifth wheel type coupling. Since this is the only connection between the vehicles, all of the force components between them pass through the pivot point. Thus all pitching and swaying loads of the trailer are transmitted through the pivot directly in the rear wheel area and the trailer follows the rear wheels in turning situations, all of which is highly desirable.
However, for non-specialized towing vehicles such as passenger cars which are very commonly used for towing horse trailers and travel trailers, this arrangement is not practical because the pivotal mounting would be located directly in the trunk, making it unusual for storing baggage and preventing closing of the trunk lid. Consequently the pivotal mounting is located outside of the car at the aft end, usually just behind the rear bumper. Thus there is a considerable overhang aft of the rear axle amounting to as much as four feet or more. The trailer imposed loads at this point produce a very pronounced leverage effect about the rear wheels, enhancing lateral sway and vertical bounce.